Radio beacon system



April 1943 w. M. HAHNEMANN 2,238,261

RADIO BEACON SYSTEM Filed May 25, 1938 2 Sheets-Sheet l INVENTOR.Ira/fer Max //a/$/7e070/7/7 BY ATTORNEY.

April 15, 1941.

W. M. HAHNE MANN RADIO B EACON SYSTEM Filed May 25, 1938 2 Sheets-Sheet2 Ire (an r1904 6274477470/P5 Patented Apr. 15, 1941 barren stares ramorrio RADKO BEACON SYSTEM Application May 25, 1938, Serial No. 209,973In Germany May 25, 1937 Claims.

The present invention relates to radio beacons adapted to produceguiding course lines for vehicles and the like, and consists in certainfeatures of novelty explained in the following description and pointedout in the appended claims, reference being made to the accompanyingdrawings in which- Fig. 1 is a diagrammatical representation of theradiation pattern obtained by radio beacon transmitters adapted toproduce a straight course line; Fig. 2 is a diagram showing radiationpatterns for obtaining a bent course line; Fig. 3 shows a plurality ofcourse lines produced according to the invention; while Fig. 4 is a planexplanatory for the invention, and Fig. 5 shows diagrammatically anarrangement of a transmitting beacon in accordance with my invention.

Radio beacon arrangements are known which produce guiding course linesby the utility of one radiating antenna which is continuously fed by ahigh frequency generator and two reflecting means which are alternatelykeyed in such manner that one reflector is effective during theineflectiveness of the other reflector. The line of equal fieldintensity thus obtained represents the guiding course line. Thiscondition is illustrated in Fig. l by way of an example. The radiatingdipole D is continuously fed by a high frequency generator which ismodulated with a predetermined tone-frequency. The reflectors RI and R2are alternately keyed in accordance with the dash-dot, or the A-N-rhythmin such manner that one reflector is rendered effective whilst thesecond reflector is rendered inefiective. The two radiation patterns AIand A2 are thus alternately produced, and the two guiding lines L! andL2 are obtained by comparison between the amplitudes of the keyedsignals of different kind. In cases that the system presents symmetricstructure, the two guiding lines LI and L2 form one single straightline. It is also possible to provide any optional angular relationbetween the two guiding lines LI and L2 by deliberately unbalancing theaforesaid symmetry which may be accomplished by exciting the tworeflectors out of phase which expedient permits the radiation to bedirected at will toward any desired point or position.

The Fig. 2 shows the last mentioned arrangement, according to which theradiating dipole is continuously supplied and the reflecting means RIand R2 are alternately rendered effective and as to obtain the desiredunsymmetry of the radiation patterns AI and A2 relative to each other.The straight 180 degree relation between the two guiding lines LI and L2is then replaced by an obtuse angle.

The radiation of more than two guiding course lines from one singlepoint is frequently required. This problem is solved according to thepresent invention by providing a radio beacon system which permits anydesired number of course lines to be radiated over an antenna systemusing one single transmitter only. The novel system comprises onecontinuously fed radiating dipole D adapted to cooperate with anydesired number of reflector sets RI, R2, and RI, RE which arealternately rendered effective. According to a further feature of theinvention either a particular keying frequency, or a dis tinctive highfrequency or even tone-frequency is allotted to each set of reflectorsfor the purpose of distinguisl'iingv the" separate course lines thusproduced. The direction of the individual course lines is determined bycorrespondingly adjusting the phases at which. the reflectors areexcited by any known means.

The operation of the new system according to the invention ishereinafter moreprecisely disclosed in conjunction with one embodimentshown in Fig. 3, and the structural diagram of Fig. 5', which by way ofan example illustrates an arrangement for producing four dilferentcourse lines. A radiating dipole D is continuously fed from a highfrequency generator TR. Two reflecting means RI and R2 forming one setof reflectors are allotted to said dipole. A further set. of reflectorsindependent of the first mentioned set and comprising the reflectingmeans RI and R2 is also allotted to the radiatinefiective exactly in themanner heretofore described. The phases of the reflector excitingvoltages may be adjusted at any desired rate so obtained, that is, onesystem comprising the radiating dipole D and theireflecting means RI andR2, and a'second" system likewise comprising said dipoleD and also-the.-reflecting means RI and R2. In cases that the flrst'mentioned system, i.e. D, RI and R2,.v is rendered effective, the directive diagrams AI andA2 and thus the course-lines LI and L2 are obtained, while theeffectiveness of the second system, that is, D, RI and R2, produces thedirective diagrams A! and" A2 and the resulting-course lines LI and L2.These two' system are alternately rendered operative by known means-suchas switching device U, and a switch SI,.;in such manner that one systemtransmits over a period of one minute, for example, during whichinterval the sec ond system remains inactive, whereupon the secondsystem operates for one minute, in which time the first mentioned systemremains ineffective.

It has been proposed according to one feature of the present inventionfor the purpose of distinguishing from one another the different courselines produced by the two alternately effective systems to allot'thereto either distinctive high frequencies, that is, variouswavelengths, or distinctive modulation frequencies, i. e. specificcharacterization tones, or even different keying frequencies, but thesimultaneous utility of more than one of the above mentioned markings ofdistinction is also within the scope of this in-, vention. Thediscrimination between the separate course lines is effected in thereceiving position and this will be accomplished in connection with thefirst mentioned method by accordingly tuning the high-frequency portionof the receiver, while on applying the second expedient this distinctionis performed by chains of filters forming part of the low-frequencyportion of the receiver. The corresponding discrimination in cases ofemploying the last mentioned method is accomplished in a simple mannerby means of acoustic comparison.

It has already been pointed out in the foregoing that the particularadvantage involved by the present invention consists in the possibilityof producing a plurality of course lines by means of one single highfrequency transmitter. In order to obtain the aforementioned course linedistinction, a switching equipment U is provided for cooperation withsaid transmitter, this equipment being adaptedto alternately applythereto either different high frequency oscillations, or differentmodulation frequencies from generators Ml, M2, or different keyingfrequencies from generator G. Moreover, additional switching means S!are provided which during the effectiveness of one reflector systemrender the remaining systems ineffective. This measure may suitably beeffectuated by making theswitching equipment of the transmitterdependent upon the switching means which during the operation of onereflector system render all remaining systems inoperative. A conjointcam-controlled device may, for example, be used for this operation. 1

According to still another feature of the invention, the separatereflecting means of reflector systems transiently in state of rest arenot necessarily to be rendered ineffective during the operation of oneparticular reflector system. Onthe contrary, individualreflecting meansmay be maintained effective so as to assist in producing the necessarydirective characteristics for obtaining radiation toward a givendirection.

. In connection with the embodiment shown in Fig. 3 it should beobserved that the dash-dotted circular radiation pattern of theradiating dipole D during ineffectiveness of the reflectors isdimensioned so as to intersect all points of inter-' section between theentire number of directive characteristics, in order to secure keyingfree of crash noises.

An arrangement of the new radio beacon sys-'- tem is illustrated in Fig.5 in which there is shown a radiating dipole D which is continu ouslyfed from the high frequency transmitter Tr over the feeder line L. Ateither side of the dipole D there are provided the reflectors RI and R2which together form a continuous guiding system. Further reflectors RIand R2 transmitter;

which likewise form a second continuous guiding system are located at agiven angle to the first mentioned system RI, R2. Each of the reflectorsincludes keying means Kl, K2 and Kl, K2, respectively. The keying meansKI and K2 on the one hand and the keying means KI and K2 on the otherhand are coupled with one another and are controlled over the line LIand L2, respectively, from the device G which generates a keyingfrequency. A switching device U has for its object to alternately rendereffective the reflector-systems RI, R2, and RI, R2, respectively, forwhich purpose a switch SI is mechanically coupledwith the switchingdevice U. The switch SI in. one position causes keying means Kl, K2 ofthe reflector system RI and R2 to be controlled over the line Ll fromkeying device G, while in the other position the keying means Kl, K2 ofreflector system RI, R2 are controlled over line L2 from G. Ifasymmetric patterns are desired, as shown in Figs. 2 and 3, suchpatterns may readily be secured by adjusting the phases of excitation ofthe reflectors in any known manner. If, for example, these reflectorsare parasitic reflectors as shown in Fig. 5, central inductance F may beadjusted to effect such tuning, asis usual in the so-called Lorenz" typesystem. A further switch S2 which is adapted to cooperate with theaforementioned switch S1 serves for changing keying frequency beingproduced by the generator G so that a different keying frequency is usedon the separate course lines. This may be accomplished in any knownmanner, e. g. by varying the release time'of relays if the keying deviceG is of the relay interrupter type or by varying the speed of rotationof a motor if this generator G is of the motor driven cam controlledtype. Finally, a third switch S3 likewise mechanically coupled with theswitching device U and the aforementioned two switches has for itsobject to alternately apply the means Ml and-=M2 to the high frequencytransmitter Tr. These means MI and M2 may be tone frequency generatorsproducing different tone frequencies by means of which the transmitterTr is modulated in dependency upon the position of the switches. On theother hand, the means MI and M2 may be devices adapted to change thecarrier frequency of the transmitter Tr, that is, the wavelengthproduced by said For example, devices MI and M2 may be carrier frequencysources of different frequency for supplying different carrierfrequencies to transmitter Tr.

The invention is by no means restricted to the arrangement for producingfour guiding course lines as described in conjunction with Figs. 3 and5. On the contrary, any desired number of reflector systems as abovedescribed may be allotted to a radiating dipole so as to produce six,eight, ten or more guiding course lines. A given distinction such as apredetermined wavelength modulating frequency or keying frequency is tobe allotted to each course line. Y Geographical and -atmosphericconditions frequently obstruct'the possibility for employing athroughout straight course" line between two air ports, in which cases;it will be necessary to proing grounds, for example. In order to obtaina guiding course line which corresponds to the route in question, and inaccordance with still a further feature of the invention, individualguiding ray transmitters of the type above described are located at thepoints or landing grounds 0 and D for producing radiations having thedesired angular relation to one another. The angle of radiation fromeach transmitter is adjustable by accordingly selecting the relativephases for keying the appertaining reflectors.

What is claimed is: p

1. A radio beacon transmitter system comprising a radiating dipoleantenna, a high frequency generator for continuously feeding saidantenna, a plurality of reflecting means arranged about said dipole andcombined to form several individual reflector systems for providingseparate angularly related guiding course lines, and means for renderingsaid reflector systems alternately eifective and ineffective.

2. A radio beacon transmitter system as defined in claim 1, furthercomprising means for transmitting a difierent given high frequency fromsaid dipole for each of said alternately efiective reflector systems.

3. A radio beacon transmitter system as defined in claim 1, furthercomprising means for providing a different specific modulatingtonefrequency to said generator for each of said alternately effectivereflector systems.

4. A radio beacon transmitter system as defined in claim 1, furthercomprising means for switching a different particular keying frequencyto control each of said alternately effective reflector systems.

5. A radio beacon transmitter system comprising a high frequencygenerator, a radiating dipole continuously fed by said high frequencygenerator and adapted to produce a circular radiating pattern, aplurality of reflecting means arranged about said dipole and to formseveral individual angularly related reflector systems, means forrendering said reflector systems alternately effective and ineffectivefor producing separate angularly related guiding course lines, and meansfor allotting to each of said alternately efiective reflector systems adistinguishing signal characteristic.

WALTER MAX HAHNEMANN.

